Motor control system with dynamic braking



Sept. 19, 1950 l. G. RILEY ErAL Mo'roR coMTRoL SYSTEM WITH DYNAMIC BRAKING 5 Sheets-Sheet 1 Filed May 22, 1948 SCP- 19 1950 L. G. RILEY ETAL.

MOTOR CONTROL SYSTEM WITH DYNAMIC BRAKING 5 Sheets-Sheet 2 INVENTORS yn/7 GJ//ey qnd eof'd 1. purl/ay,

' ATTOR Y Filed May 22, 1948 Sept. 19, 1950 L G. RILEY ErAL 2,523,143

MoToR CONTROL SYSTEM WITH DYNAMIC BRAKING Filed May 22, 1948 5 Sheets-Sheet 3 ATTORN Sept. 19, 1950 L. G. RILEY ETAL MOTOR CONTROL SYSTEM WITH DYNAMIC BRAKING 5 Sheets-Sheet 4 Filed May 22, 1948 Ano/@eres fmf@ M Sept. 19, 1950 L G. RILEY ErAL MOTOR CONTROL SYSTEM WITH DYNAMIC BRAKING Filed May 22, 1948 5 Sheets-Sheet 5 Patented Sept. 19, 1950 MOTOR CONTROL SYSTEM WITH DYNAMIC BRAKIN G Lynn G. Riley and George R. Purifoy, Pittsburgh,

Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application Maly 22, 1948, Serial No. 28,618

18 Claims.

Our invention relates, generally, to control systems, and, more particularly, to systems for controlling the operation of the propelling motors of electric vehicles.

An object of our invention,A generally stated, is to provide a motor control system which shall be simple and eflicient in operation and which may be economically manufactured and installed.

A more specific object of our invention is to provide for positioning orv spotting control equipment of the unit-switch type in accordance with the vehicle speed during coasting to secure smooth deceleration of the vehicle when dynamic braking is applied.

Another object of our invention is to provide for automatically controlling the operation of a multiple-notch Iield shunting controller.

A further object of our invention is to secure a quick build up of the dynamic braking effect by automatically increasing the motor eld strength.

Still another object of our invention is to prevent overspeeding of a vehicle by obtaining some dynamic braking effect during coasting of the vehicle.

Other objects of our invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with our invention, both the acceleration and the deceleration of a vehicle are automatically controlled by control equipment of the unit-switch type. A power operated controller provides multiple-notch eld control and the equipment is spotted during coasting by motor eld regulation in preparation for the application of dynamic braking. Building up of the dynamic braking elect is obtained by automatically controlling the operation of the field shunting controller to increase the motor eld strength.

For a better understanding of the nature and objects of our invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings, in which:

Figures 1A and 1B, when combined, constitute a diagrammatic View of a control system embodying the principal features of our invention;

Fig. 2 is a schematic diagram showing the main circuit connections for the motors and the control apparatus;

Fig. 3 is a chart, showing the sequence of operation of part of the apparatus illustrated in Figs. l and 2;

Fig. 4 is a typical acceleration notching curve for a motor of the type utilized lin the present system, and

Fig. 5 is a typical dynamic braking notching curve for the motor.

Referring to the drawings, two motors MI and M2 may be utilized for `propelling an electric vehicle, such as, for example, a subway car (not shown). The motors are of the series type having armature windings II and I2 and series field windings I3 and I4, respectively. vA line switch LSI is provided for connecting the motors to a current collecting device I5 which engages a trolley conductor I6, A switch G is provided for connecting the motors to a ground connection I l, thereby completing the circuit to a source of power, such as a power generating station (not shown).

As indicated in the sequence chart in Fig. 3, the motors MI and M2 are rst connected in series-circuit relation and then in parallel-circuit relation during acceleration of the vehicle. In addition to the switches LSI and G, a switch JR. is provided for connecting the motors in series-circuit relation. Bridging transition of the motors is obtained by means of a switch J which is closed during the transition period. The parallel-circuit connections are established through the switches LSI, G and a double pole switch MG. A switch L82 is provided for shunting a resistor I 8 from the motor circuit on the second notch or step of the accelerating cycle, as indicated in the sequence chart. The switch J shunts a resistor 20 from the motor circuit just prior to the transition from series to parallel operation.

The motors may also be connected for dynamic braking with the eld winding I4 connected across the armature winding II and the eld winding I3 connected across the armature winding I2, thereby permitting the current in the armature windings to reverse and cause the m0- tors to act as generators and retard the vehicle. In addition to the switch MG which is closed during dynamic braking, switches BI, B2, B3, B4, B5 and B6 are utilized to establish the dynamic braking circuits and to control the motor' current by shunting a resistor I 9 from the motor circuits during dynamic braking.

The motor current during both acceleration and dynamic vbraking is controlled by resistors :2| and 22. Double pole resistor shunting switches RI, R2, R3, R4 and R5 are provided for shunting the resistors 2I and 22 step-by-step. The resistor shunting switches operate in sequential relation, the sequence being controlled by interlock progression in a manner well known in the art.

The operation of the resistor shunting switches is automatically controlled by a current responsive relay CR having a series coil which is connected in the motor circuit during both acceleration and dynamic braking. In addition to the series coil, the relay CR is provided with a rate coil RC which is energized through an adjustable resistor 23 during acceleration and through a variable rheostat 24 during dynamic braking. If desired, the resistor 23 may be adjusted by a variable load mechanism, in accordance with the load on the vehicle, in a manner well known in the art.

As indicated in the drawings, the rheostat 24 may be adjusted by means of a braking kcontroller BC which is operated during dynamic braking. If desired, the rheostat 24 may be adjusted in the manner described in Patent No. 2,318,330 issued May 4, 1943 to G. R. Purifoy, thereby coordinating the operation of the air brake system and the dynamic braking of the vehicles. As described in the aforesaid patent, an air operated device is provided on each vehicle of a train for actuating the rheostat on each vehicle. These devices are connected to the air line of the air brake system and each device is, therefore, responsive to the air brake pressure which, in turn, is controlled by the braking controller BC. In order to simplify the present drawings, the air line connections have been omitted.

The relay CR is also provided with a braking rate coil BRC which is connected across a portion of a resistor 25 which is connected in the motor circuit during dynamic braking. Thus, the calibration of the relay CR is changed during dynamic braking by the effect of the coil BRC. P

An accelerating controller AC is provided for controlling the operation of the motor connecting switches during acceleration of the vehicle. The controller AC may be of the drum type and, as shown, is provided with four positions, namely, oit, switching, series, and parallel.

In order to permit the present system to be utilized on cars which are operated in multiple unit trains and controlled from one control station at the head of the train, a braking relay BR is provided. The relay BR permits dynamic braking to be established simultaneously on all the cars of a train. The energization of the relay BR is controlled by the braking controller BC which, as explained hereinbefore, may also be operated to control the air brake system which has not been shown. Thus, when the braking controller at the head of the train is operated, all of the relays BR, throughout the train are energized to cause dynamic braking to be established on all the motors in the train. rIhe controllers AC and BC are electrically interlocked to prevent improper operation of the equipment.

Provision is made for shunting the series field windings of the motors during portions of the accelerating and the braking cycles by means of multiple step controllers FCI and FCZ. As shown, the controllers FCI and FCZ may be actuated by an air engine FC which is provided with magnet valves SF and FFvfor controlling the uid pressure in the air engine.

The shunt circuit for the field winding I3 comprises a resistor 26 and a reactor 2`I. As shown, the resistor 25 may be shunted step-by-step by means of the controller FCI. The shunt circuit for the series field winding I4 comprises a resistor 28V and a reactor 29. The resistor 28 may be shunted step-by-step by the controller FCZ. As explained hereinbefore, the controllers FCI and FCZ may be operated simultaneously by the air 4 engine FC. The controller FCI is provided with auxiliary contact segments 3|, 32, 33 and 34, the function of which will be explained more fully hereinafter.

In the power oi or coasting position of the controller AC, the dynamic brake circuits are established and, at any speeds below a predetermined speed, the field shunt notching will progress at a low braking current under the control of a spotting relay SR. As shown, the actuating coil of the relay SR is connected across a portion of the resistor 25 which is in the dynamic braking circuit. Thus, the relay SR is responsive to the vehicle speed since the voltage drop across the resistor 25 varies with the current through the resistor which, in turn, is proportional to the vehicle speed. Therefore, the control equipment is positioned in accordance with the car speed and is prepared to respond promptly whenever a brake application is called for. The spotting relay controls the operation of the eld shunting controller FC during the spotting operation.

While the basic spotting system aiects only the position of the field shunt controller, spotting may take place on any of the series resistor notches depending on the shut 01T speed and the length of the coasting period. In general, the spotting relay will select the proper notch, depending on the eld strength required to get spotting current response. Two way spotting of the field controller insures proper positioning of the equipment within a short time after closing the coasting circuits. Brake response is secured by building up eld strength and by resistor notches, depending on the braking rate desired. A time delay relay TD is provided for delaying the operation of the resistor shunting switches for a short time interval after full dynamic braking is called for in order to insure that the eld strength of the motors has had time to build up.

In order that the functioning of the foregoing apparatus may be more clearly understood, the operation of the system will now be described in more detail. Assuming that it is desired to accelerate the vehicle at the maximum rate, the controller AC is actuated to the parallel position, thereby obtaining automatic operation of the control equipment.

When the controller AC is on the switching position, the switches LSI, G and JR are closed to connect the motors MI and M2 in series-circuit relation and in series with the resistors IB, 2i and 22. The energizing circuit for the actuating coil of the switch LSI may be traced from positive at the controller AC through segments 35, 38 and 31, conductor 38, an interlock BI3, conductor 39, an interlock B56, conductor 4I and the actuating coil of the switch LSI to negative. The energizing circuit for the actuating coil of the switch G extends from the controller segment 36 through conductor 42, an interlock B24, conductor 43 and the coil of the switch G to negative. Following the closing of the switches LSI and G, the actuating coil of the switch JR is energized through a circuit which extends from the controller segment 35 through an interlock LSI3, conductor 44, an interlock G3, conductor 45, an interlock MG3, conductor 46, an interlock J4, conductor 4'I and the coil of the switch JR to negative.

The closing of the switches LSI, G and JR connects the motors in series-circuit relation through a circuit which extends from the current collecting device I5 through the switch LSI, the resistor I8, conductor 48, the armature winding II of the motor MI, conductor 49, the series coil of the relay CR, conductor 5I, a reversing switch 52, the series field winding I3, the reversing switch 52, conductor 53, the resistor 2l conductor 54, ythe switch JR, the resistors and 22, conductor 55, a reversing switch 56, the eld winding I4; the reversing switch 56, conductor 51, the armature winding I2, conductor 58 and the switch G to ground at I1.

When the controller AC is on the series positionthe switch LSZ is closed to shunt the resistor I8 -from the motor circuit. The energizing circuit forthe actuating coil of the switch L82 may be traced from a controller segment 59 through an interlock LSI 4, conductor 6I, an interlock JR3, lconductor 62, an interlock LS23, conductor 63 and the coil of the switch LSZ to negative. A holding circuit for the coil of the switch LS2 is established from the conductor 38 through an interlock LS22 when the switch is closed.

* Following the closing of the switch LS2, the resistor shunting switches RI R2, R3, R4 and R5 are closed in sequential relation under the conl tro'lfof the limit relay CR. The energizing circuit fo'rltheactuating coil of the switch RI extends from' the conductor 6I through an interlock LS24, yconductor B4, the contact members of the relay ACR, conductor 65, an interlock LSI5, conductor 66an interlock LSZI, conductor 61, an interlock R13 andthe actuating coil of the switch RI to negative. A holding circuit is established from the conductor 45 through aninterlock LSI I, con- Alf'iuctor andan interlock RI2 when the switch is closed.

*As 'explained hereinbefore, the switches R2, R3, R4 'and'R5 are closed by interlock progression under the control of the limit relay CR. The energizing circuit for the actuating coil of the 'switch R2 extends from theconductor 66 through "interlocks RI i 'and R23, the coil of the switch R2, finterlocksR3I,vR4l and R5I, conductor 69 and an interlock J I to negative; -A holding circuit for the'switch R2 is lestablished from lthe conductor `68 through an interlock R24 on the switch R2. Fllo'wing 'the closing of the Switch R2, the actuating coil of the switch R3 is energized through a circuit which extends from the con- 'ductor' 65 rthrough an interlock R22,` the coil of the switch R3',` the interlocks R4I, R5I, the conductor 69 and the interlock J I tofnegative. A holdingI circuit for the switch R3 is established through an interlock R34'.

i The actuating coil of the switch R4 is energized 'through a circuit which extends from the conductor 66? through interlocks R2I and R33, the coil 'of the switch R4, interlock `R5I, conductor 69 and the interlock J I to negative." A holding circuit for the switch R4 is established through an interlock R43.

The actuating coil 'of the switch`R5 is energized from-the conductor 66 through interlocks `R32 and R42, the coil of the switch R5, conductor '69 and the' interlock J I to negative. It will be lnoted that the closing 'of the' switch R5 opens the interlock R5I, thereby causing the switchr R4 to open'. The switch R3 was openedv following the closingof the switch R4 and the switch R2 was opened following the closing of 'the switch R3 by the yopening of the interlocks on the proper switches. Arholding circuit for the switch R5 I*is established Athrough an interlock R52 when `ther'switch is closed. 'f-Following the` closingofl the kswitch R5, lthe switch J is closed during bridging,V transition of the motors from series-circuit relation to parallel-circuit relation. The energizing circuit for the actuating coil of the switch J extends from the conductor 66 through an interlock R44, conductor 1|, an interlock R54, conductor 12, an interlock MG4, conductor 13, and the coil of the switch J to negative. A holding circuit for the switch J extends from the conductor 45 through lan interlock J3, conductor 12, the interlock MG4, conductor 13 and the coil of the switch J to negative. The closing of the switch J causes the opening of the switch JR by interrupting the energizing circuit for the coil of the switch JR which was previously established through the interlock J4 on the switch J. As explained hereinbefore, the switch J shunts the resistor 20 from the motor circuit.

At this time the switch MG is closed to cornplete the parallel connections for the motors MI and M2. The energizing circuit for the actuating coil of the switch MG may be traced from positive through the controller segment 35, conductor 14, an interlock R53, conductor 15, an interlock J 2, conductor 16, and interlock J RI, conductor 11 and the coil of the switch MG to negative. A holding circuit is established from the conductor 45 through an interlock MGZ to the coil of the switch MG. The closing of the switch MG causes the opening of the switch J by interrupting the holding circuit through the interlock MG4.

The motors MI and M2 yare now connected in parallel-circuit relation. The circuit through the motor MI extends from the conductor 48 through the armature winding Il, conductor 49, the series coil of the relay CR, conductor 5I, the reversing switch 52, eld winding I3, theswitch 52, conductor 53, the resistor 2|, conductor^54, the switch MG, conductor 5S and the switch G to ground at I1. The circuit for the motor M2 extends from the conductor 48 through the switch MG, conductor 18, the resistor 22, conductor 55, the reversing switch 56, the field winding I4, the switch 55, the armature rwinding I2, conductor 58 and the switch G to ground. Y f

The acceleration of the motors, is continued by the closing of the switches R2, R3, R4 and R5 to shunt the resistors 2| and 22 from the motor circuit. The resistor shunting switches are operated in sequential rel-ation under the control of the relay CR in the manner previously described.

Following the closing of the switch R5, the actuating coil of the magnet Valve SF is energized to actuate the field shunting controllers FCI and FCZ from the full eld position to the short eld position, thereby shunting the motor elds to increase the speed of the motors. During series operation of the motors, the magnet valve FF was energized through 'a circuit extending from the conductor 68 through an interlock JR2, conductor 19 and the coil FF to negative.

Istrength of the motors and causing the speed Aof the motors to increase in a manner well known in the art. When the eld shunting controllers are on the short eld position, the accelerating .cycle is completed.

If it is desired to permit the vehicle to coast, :the controller AC is actuated to the oil position, thereby causing the opening of the switches LSI, LS2 and G to disconnect the motors from the power source. Following the opening of the switches LSI and G, thel switch BI is closed to establish dynamic braking circuits for the motors. The energizing circuit for the actuating coil of the switch BI may be traced from a segment 84 `on the controller AC through conductor 35, an -interlock LSIZ, conductor l', an interlock GI, conductor B5, an interlock B52, conductor 8'I, the vactuating coil of the switch BI, conductor 88, an interlock B I, conductor 89 and an interlock MGI to negative.

At this time the motors are connected for dynamic braking with the resistors I9, 2| and 22 connected in the dynamic braking circuits and with the eld controllers FCI and FC2 on the Ashort -field position to shunt the motor field Windings. Since the motors are operating with a weak field strength and the maximum amount of external resistance is connected in the dynamic .braking circuits, a relatively small amount of braking current circulates through .the motors. However, this current is enough to give suflicient braking action to prevent the vehicle from attaining an excessive speed during coasting.

The dynamic braking circuit for the motor MI ,extends from one terminal of the armature Ywinding II through conductor 48, the switch MG, conductor 1B. the resistor 22, conductor 55, the reversing switch 56, the field winding I4 of the motor M2, the switch 5B, conductor 5l, the Switch BI, the resistor I9, conductor 9|, the resistor 25 and conductor 49 to the other terminal of the varmature winding II. The circuit for the motor M2 extends from one terminal of the armature winding I2 through conductor 51, the switch BI, the resistor I9, conductor 9|, the resistor 25, conductor 49, the series winding of the relay CR,

conductor 5l, the reversing switch 52, the held winding I3 of the motor MI, the switch 52, conductor 53, the resistor 2|, conductor 54, the .switch MG and conductor 58 to the other terminal of the armature winding I2.

During coasting of the vehicle the operation of the eld shunting controllers FCI and FC2 and the resistor shunting switches is under the control of the spotting relay SR which, as explained hereinbefore, is responsive to themotor speed. In this manner, the control apparatus is Ipositioned in accordance with the car speed and is prepared to respond promptly whenever a brake application is called for.

As explained hereinbefore, the field shunting controllers FCI and FC2 were actuated to the short eld position during acceleration of lthe motors. They remain in this position during coasting until the braking current decreases sufficiently to permit the spotting relay SR to drop to its lowermost position.

When the relay SR is in its lowermost position, an energizing circuit is established for the magnet coil FF, thereby causing the eld controllers FCI and FC2 to be actuated from the short iield position toward the full eld position. The enconductor 92, contact members SRI of the relay SR, conductor 93, contact segment 33 ofthe coniii() `of the resistor I9 v:from the motor circuits.

8 ltroller FCI, conductor 'I9 and the coil FFitonegftive.

In this manner the eld controller is actuated toward the full eld position under the control of the spotting relay SR. When the field controller reaches the F2 position, the switch B2 is closed to shunt a, portion of the resistor I9 lfrom the motor circuits. The energizing circuit for the actuating coil of the switch B2 may be traced from the conductor 93 through contact members BR3 of the relay BR, conductor 94, contact segment 34 of the controller FCI, conductor 95, an

interlock B I 2, conductor 96, an interlock B2 I, the

actuating coil of the switch B2, conductor 8B, the interlock B5I, conductor 89 and the interlock MGI to negative. A holding circuit lis established from the conductor 86 through an interlock B22.

The shunting of a portion of the resistor I5 from the motor circuits will, of course, cause the motor current to increase, thereby actuating the relay SR to its uppermost position. When the relay SR is in its uppermost position, an energizing circuit is established for the magnet coil SF, thereby causing the iield controllers FCI and FC2 to be operated toward the short field position. The circuitforthe coil SF extends from the conductor 92 through contact members SR2, conductor 91,-the contact segment 3I and conductor 83 through the coil SF to negative.

The iield controller is stopped on position F4 by the interrupting of the circuit through the .contact segment 3| and remains on this position until the motor current decreases suiciently to rpermit the Vrelay SR to drop to its lowermost position. When the relay drops to its lowermost position, the energizing circuit for the magnetrcoil FF is reestablished, thereby causing the field controller to be actuated toward the full field position.

When the iield controller reaches position F2, the switch B3 is closed to shunt another portion The energizing circuit for the actuating coil of the switch B3 extends from the conductor 95 through interlocks B23 and B3I to the coil of the switch B3 and thence through conductor 98, the interlock BSI, conductor 89 and the interlock MGI to negative.

In this manner the resistor shunting switches are spotted during coasting bythe operation of the field controller which, in turn, is under the control of the spotting relay SR. The switches B4, B5 and B6 may be closed by interlock progression under the control of the spotting relay in a. similar manner. If the vehicle speed continues to decrease during coasting, the switches vRI to`R5 will be closed under the control ofthe spotting relay, thereby continuing to shunt resistancefrorn the motor circuit in accordance with the vehicle speed.

If it is desired to decelerate the vehicle by dynamic braking, the controller BC is actuated to establish an energizing circuit for the actuating coil of the relay BR. This circuit extends from the conductor through a segment 98 on the controller BC, conductor 99 and the coil of therelay BR to negative.

When the relay BR is actuated to its uppermost position, the contact members BH3 and BR4 are opened and a contact member BRI is closed, thereby transferring the control of the resistor shunting switches and the eld shunting controller from the spotting relay SR to the current responsive relay CR. At this time a Contact member BRS is `also closed to energize y,the ;rate

coil RC on the relay CR through a circuit which' extends from positive through a contact member BR5, conductor IDI, the rheostat 24, conductor |02 and the coil RC to negative.

It will be noted that the circuit through the variable resistor 23 was interrupted by the opening of an interlock LS26 when the switch LS2 was opened at the beginning of the coasting operation. As explained hereinbeforc, the rheostat 24 is adjusted in accordance with the position of the controller BC, thereby governing the dynamic braking rate by changing the calibration of the relay CR.

The closing of the contact member BR on the relay BR also energizes both the magnetizing coil M and the neutralizing coil N of the time delay relay TD, thereby actuating this relay to its upV permost position. The energizing circuit for the magnetizing coil extends from the conductor IUI through the segment 32 on the controller FCI, conductor |03 and the coil M to negative. The circuit for the neutralizing coil extends from the conductor IUI thro-ugh a resistor |04 and the coil N to negative.

At this time the field shunting controller is actuated toward the full eld position to increase the field strength of the motors, thereby building up the dynamic braking effect. The energizing circuit for the magnet coil FF extends from the conductor 65 through a contact member BRZ of the relay BR, conductor |05, the segment 33 on the controller FCI, conductor 19, and the coil FF to negative. When the eld shunting controller is on position FI, the circuit through the segment 33 is interrupted, thereby stopping the field shunting controller on position FI. At this time the circuit through the segment 32 for the magnetizing coil M of the time delay relay TD is also interrupted. The eld shunting controller is held on position FI for a short time interval while the neutralizing coil N of the time delay relay demagnetizes the relay suiciently to permit it to drop to its lowermost position. The delay in the operation of the eld shunting controller is to insure that the neld strength of the motors has time to build up before the operation of the resistor shunting switches is begun. e

When the Contact member TDI on the relay TD is closed, within a short time after the deenergization of the magnetizing coil M, the magnet coil FF is energized through a circuitfwhich extends from the conductor |05 through the contact member TDI, conductor 'i9 and the coil FF to negative. The eld shunting controller is then actuated to the full field position.

When the eld shunting controller is on position FF, the progression wire 95 for the re-r sistor shunting switches B2 to B6 is energized through a. circuit which extends from the conductor |05 through contact members TD2, conductor |06 and the segment 34 on the controller FCI. 95 causes the switches B2 to B6 to be operated in the order shown in the sequence chart in Fig. 3 to complete the shunting of the resistor I9 from the motor circuits. y

It will be understood that the sequential operation of the resistor shunting switches starts from the last switch which was closed during the coasting operation under the control of the spotting relay. Thus, the amount of resistance in the motor circuit has been proportioned according to the vehicles speed and a smooth dynamic braking effect is obtained without delay when the full dynamic brake is applied.

The energization of the progression wirer When the switches have been closed to com; plete the shunting of the resistor I9 from the motor circuit under the control of the relay CR,- the switches RI to R5 are closed in the order shown in the sequence chart in Fig. 3 to shunt the resistors 2| and 22 from the motor circuit. The progression wire 66 for the switches RI to R5 is energized through an interlock G2 on the switch G. The resistor shunting switches are operated by interlock progression under the control of the relay CR in the manner hereinbefore described.-

When the switches are closed to shunt the resistors 2| and 22 from the motor circuit, the dynamic braking cycle is completed and the vehicle may be brought to a standstill by means of the air brake system. As described in Patent 2,345,150, issuedfMarch 28, 1944 to G. R. Purifoy,

the dynamic braking and the air brake systemv may be so coordinated thatvthe air brake system takes effect as the dynamic braking system fades out, thereby continuing the deceleration of the vehicle in a smooth manner.

The sequential operation of the switches BI to B by interlock progression has not been described in detail since it is similar in principle. to the operation of the switches RI to R5 which has been described in detail. The interlocks onv the switches and the circuits which control their operation are shown in the diagram and the switches are operated in the order shown in the sequence chart in Fig. 3. Other protective interlocks shown in the diagram have not been described in detail since their function and method of operation are well known in the railway control art.

From the foregoing description it is apparent that we have devised a control system of the unit switch type which provides for the positioning.

or spotting ofthe control equipmentduring coasting in preparation for a prompt brake application. The building up of the dynamic braking load is obtained by increasing the motoriield strength which is done prior to the operation of 3 the resistor shunting switches thereby insuring the proper operation of the equipment. The system herein described is particularly suitable for utilization on subway cars which are operated in multiple-unit trains, but is not necessarily limited thereto.

Since numerous changes may be made in the above described construction and different embodiments of the invention may be made without departing from the spirit andscope thereof, it is intended that all matter contained in the fore# going description or shown in the accompanying` drawings shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

l. In a control system, in combination, a motorv having a series field winding, power conductors,v switching means for connecting the motor to the power conductors, resistance meansk for controlling the motor current, a plurality of unitswitches operable in sequential relation byinter. lock progression to shunt said resistance means step-by-step, a relay responsive to the motor current for controlling the operation of said switches,

a multiple-notch controller for shunting the' series field winding, and interlocking means actuated by certain of said resistor shunting unit switches for controlling the operation of said eld shunting controller. N

2.l In a control system, in combination, a motor having a series Iield winding, power conductors',`

switching meansfor connecting' the motor.' to. the p'ower conductors, resistance means. for controlling the motor current, a plurality of unit ated` by certain of said resistor shunting unit switches and cooperating with said relay to control the operation of said iield shunting controller.

3; In a control system, in combination, a motor having a series eld winding, power conductors, switching means for connecting the motor to the power conductors, resistance means for controlling the motor current, a plurality of unit switches operable in sequential relation by interlock progression to shunt said resistance means step-by-step, a. relay responsive to the motor current for controlling the operation of saidl switches, a multiple-notch controller for shunting the series eld winding, power means for operating said controller in either direction, and interlocking. means actuated by certain of said resistor shunting unit switches for controlling the opera-y tion of said controller.

4; In a control system, in combination, a motor having a series eld winding, power conductors, switching means for connecting the motor to the power conductors, resistance means for controlling the motor current, a plurality of unit switches operable in sequential relation by interlock progression to shunt said resistance means step-by-step, a relay responsive to the motor current for controlling the operation of said switches, a multiple-notch controller for shunting the series eld winding, power means for operating said controller in either direction, and interlock-- ing means actuatedI by certain of said resistor shunting unit switches and cooperating withsaid relay to control the operation of said controller.

5. In a control system, in combination, a plurality of motors having series field windings, power conductors, switching means for connecting the motors to the power conductors in series-circuit relation, additional switching means for connecting the motors in parallel-circuit relation, resistance means for controlling the motory current, a plurality of unit switches operable in sequential relation by interlock progression to shunt said resistance means' step-by-step, a relay responsive to the motor current for controlling the operation oi said switches, a multiple-notch controller for shunting the` series eld windings, and interlocking means actuated by said switching means and certain of said resistor shunting unit switchesv for controlling the operation of said controller.

6. In a control system, in combination, a plurality of motors having series iield windings, power conductors, switching means for connecting the motors to the power conductors in seriescircuit relation, additional switching means for connecting the motors in parallel-circuit relation, resistance means for controlling the motor current, a plurality of switches operable in sequential relation to shunt saidl resistance means step-by-step, a relay responsive to the' motor current for controlling the operation of said switches, a multiple-notch controller for shunting the series field windings, power means for operating said controller in either direction, in-

terlockin'g means actuated by theA series connectingV switching means for controlling said power means to operate the controller in one direction, and interlocking means. actuated by the parallel connecting switching means for controlling said power means to operate the controller in the opposite direction.

7l. In a control system, in combination, a motor having a series field winding, power conductors, switching means for connecting the motor to the power conductors, additional switching means for establishing dynamic braking connectionsV for the motor, said dynamic braking connections being established during coasting of the motor, resistance means for controlling the motor current, a plurality of' switches for shunting said' resistance means step-by-step, a multiple-notch controller for shunting the series eld winding, a relay responsive to the motor speed for controlling the-operation of said controller during coasting of the motor, and auxiliary switching means on said controller for controlling the operation of said resistor shunting switches.

8. In a control system, in combination, a motor having a series eld winding, power conductors, switching means for connecting the motor to the power conductors, additional switching means for establishing dynamic braking connections for the motor, said dynamic braking connections being established during coasting of the motor, resistancemeans for controlling the motor current, a plurality of switches for shunting said resistance means step-by-step, a multiple-notch controller for shuntingthe series field winding, a relay responsive to the motor speed for controlling the operation of said controller during coasting of the motor, and auxiliary switching means actuated by said controller and cooperating with said relay to control the operation of said resistor shunting switches.

9. In a control system, in combination, a motor having a series iield winding, power conductors, switching means for connecting the motor to the power conductors, additional switching means for establishing dynamic braking connections for the motor, said dynamic braking connections being established during coasting of the motor, resistance means for controlling the motor current, a plurality of unit switches operable in sequential relation by interlock progression for shunting said resistance means step-by-step, a multiple-notch controller for shunting the series iield winding, power means for operating said controller in either direction, and a relay responsive to the motor speed for controlling the operation of said controller in either direction during coasting of the motor.

l0'. In a control system, in combination, a motor having a series eld winding, power conductors, switching means for connecting the motor to the power conductors, additional switching means for establishing dynamic braking connections for the motor, said dynamic braking connections being established during coasting of the motor, resistance means for controlling the motor current, a plurality of switches for shunting said resistance means step-by-step, a multiple-notch controller for shunting the series eld winding, power means for operating said controller in either direction, a relay responsive to the motor speed for controlling the operation of said controller in either direction during coasting of the' motor, and auxiliary switching means on said controller forV controlling the operation of said resistor shunting switches;

1l. In a control system, in combination, a motor having a series field winding, power conductors, switching means for connecting the motor to the power conductors, additional switching means for establishing dynamic braking connections for the motor, said dynamic braking connections being established during coasting of the motor, resistance means for controlling the motor current, a plurality of switches for shunting said resistance means step-by-step, a multiple-notch controller for shunting the series field winding, power means for operating said controller in either direction, a relay responsive to the motor speed for controlling the operation of said controller in either direction during coasting of the motor, and auxiliary switching means actuated by said controller and cooperating with said relay to control the operation of said resistor shunting switches.

12. In a control system, in combination, a motor having a series eld winding, power conductors, switching means for connecting the motor to the power conductors, a, manually operable controller for controlling the operation of said switching means, additional switching means for establishing dynamic braking connections for the motor when said controller is operated to open said first-named switching means, resistance means for controlling the motor current, a plurality of switches for shunting said resistance means step-by-step, a relay responsive to the motor current for controlling the operation of said switches, a relay responsive to the motor speed for also controlling the operation of said switches, and manually controlled means for transferring the control of said switches from one of said relays to the other.

13. In a control system, in combination, a motor having a series field winding, power conductors, switching means for connecting the motor to the power conductors, a manually operable controller for controlling the operation of said switching means, additional switching means for establishing dynamic braking connections for the motor when said controller is operated to open said rst-named switching means, resistance means for controlling the motor current, a plurality of switches for shunting said resistance means step-by-step, a relay responsive to the motor current for controlling the operation of said switches, a relay responsive to the Amotor speed for also controlling the operation of said switches, and a manually operable braking controller for causing the transfer of the control of said switches from one of said relays to the other.

14. In a control system, in combination, a motor having a series field winding, power conductors, switching means for connecting the motor to the power conductors, a manually operable controller for controlling the operation of said switching means, additional switching means for establishing dynamic braking connections for the motor when said controller is operated to open said first-named switching means, resistance means for controlling the motor current, a plurality of switches for shunting said resistance means step-by-step, a relay responsive to the motor current for controlling the operation of said switches, a relay responsive to the motor speed for also controlling the operation of said switches, a manually operable braking controller for causing the transfer of the conv tions for the motor, resistance means for controlling the motor current, a plurality of switches for shunting said resistance means step-by-step, a multiple-notch controller for shunting the series eld winding, a relay responsive to the m0- tor current for controlling the operation of said controller and said resistor shunting switches,

i and timing means for delaying the operation of said controller for a predetermined time interval.

16. In a control system, in combination, a motor having a series eld winding, switching means for establishing dynamic braking connections for the motor, resistance means for controlling the motor current, a plurality of switches for shunting said resistance means step-bystep, a multiple-notch controller for shunting the series field winding, a relay responsive to the motor current for controlling the operation of said controller, auxiliary switching means on said controller for controlling the operation of said resistor shunting switches, and timing means for delaying the operation of said controller for a predetermined time interval.

17. In a control system, in combination, a motor having a series field winding, switching means for establishing dynamic braking connections for the motor, resistance means for controlling the motor current, a plurality of switches for shunting said resistance means stepby-step, a multiple-notch controller for shunting the series field Winding, a relay responsive to the motor current for controlling the operation of said controller, auxiliary switching means on said controller for controlling the operation of said resistor shunting switches, and timing means cooperating with said auxiliary switching means to control the operation of said controller.

18. In a control system, in combination, a motor having a series field winding, switching means for establishing dynamic braking connections for the motor, resistance means for controlling the motor current, a plurality of switches for shunting said resistance means step-by-step, a multiple-notch controller for shunting the series eld winding, a relay responsive to the motor current for controlling the operation of said controller, auxiliary switching means on said controller for controlling the operation of said resistor shunting switches, timing means cooperating with said auxiliary switching means to control the operation of said controller, and a manually operable braking controller for controlling the energization of said timing means.

LYNN G. RILEY. GEORGE R. PURIFOY.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 2,066,920 Willby et al Jan. 5, 1937 2,078,684 Riley Apr. 27, 1937 2,198,481 MacDonald et al. Apr. 23, 1940 

